1. Field of the Invention
The present invention relates to an improvement in an operating mechanism of an iris diaphragm device.
2. Description of the Prior Art
Recently, there have been widely used endoscopes which are capable of observing the organ in the cavity or the like by inserting its elongated insertion portion into the cavity and, if necessary, performing a variety of medical curing operations by using a selected curing device in such a manner that the curing device is inserted into a channel formed in the endoscope.
When the endoscope is used to observe the organ or the like, the quantity of irradiating light or the quantity of light received by the observing means is automatically adjusted so that a subject image of a proper brightness level is always be obtained. As a means for adjusting the quantity of light, a mechanical iris diaphragm device for adjusting the quantity of irradiating light is usually employed in a light source device for supplying irradiating light to the endoscope. However, it might by considered feasible to employ a structure which is arranged in such a manner that a mechanical iris diaphragm device for adjusting the quantity of irradiating light or the quantity of light received by the observing means is disposed at the front portion of the insertion portion of the endoscope.
The mechanical iris diaphragm device is, as disclosed in Japanese Patent Publication No. 1986-54779, operated in such a manner that an electric motor serving as an operating means is rotated so as to operate aperture blades via a transmission mechanism such as a gear. Furthermore, a mechanism arranged in such a manner that the aperture blades are operated by an electromagnet serving as the operating means has been disclosed in Japanese Patent Publication No. 1981-9692. In addition, another structure arranged in such a manner that a bimorph device is used as the operating means has been disclosed in Japanese Utility Model Publication No. 1989-88930.
However, the structure of the iris diaphragm device becomes too complicated in the case where the electric motor or the electromagnet is employed as the operating device for the iris diaphragm device. Therefore, the size of the iris diaphragm device cannot be sufficiently reduced so as to have the iris diaphragm device included in the front portion of the insertion portion of the endoscope. Since the bimorph device employed as the operating means for the iris diaphragm device as disclosed in Japanese Utility Model Publication No. 1989-88930 cannot sufficiently displace the aperture blades, a transmission mechanism for enlarging the quantity of displacement is necessary to be provided between the bimorph device and the aperture blades. Therefore, also the size of the iris diaphragm device cannot be reduced satisfactorily.